Polysomnography is a sleep study. A sleep study monitors you as you sleep, or try to sleep.
There are two states of sleep:
Rapid eye movement (REM) sleep is when you dream. Your muscles (except your eyes and breathing muscles) do not move during this stage of sleep.

Non-rapid eye movement (NREM) sleep has four stages that can be detected by brain electrical activity (EEG) waves.

REM sleep alternates with NREM sleep about every 90 minutes. A person with normal sleep usually has four to five cycles of REM and NREM sleep during a night.

A sleep study measures your sleep cycles and stages by recording:
Air flow in and out of the lungs during breathing
Blood oxygen levels
Body position
Brain waves (EEG)
Breathing effort and rate
Electrical activity of muscles
Eye movement
Heart rate

How the Test Is Performed
AT A SLEEP CENTER
The most common type of sleep study is performed at a special sleep center. You will be asked to arrive about 2 hours before bedtime. You will sleep in a bed at the center.

Many sleep centers have rooms that are similar to hotel rooms, so that you are in a comfortable bedroom. The test is often done during the night so that your normal sleep patterns can be studied.

The health care provider will place electrodes on your chin, scalp, and the outer edge of your eyelids. These must remain in place while you sleep.

Signals from the electrodes are recorded while you are awake (with your eyes closed) and during sleep. The time it takes you to fall asleep is measured, as well as the time it takes you to enter REM sleep.

Monitors to record your heart rate and breathing will be attached to your chest. These also must stay in place while you sleep. A specially trained health care provider will observe you while you sleep and note any changes in your breathing or heart rate. The number of times that you either stop breathing or almost stop breathing will be measured.

In some sleep study centers, a video camera records your movements during sleep.

AT HOME
Portable sleep study devices that can be used in the home instead of at a sleep center are available to help diagnose sleep apnea. You go to a sleep center to pick up the device, or a trained therapist comes to your home to set up the device.
Portable devices are best used when:

You are under the care of a sleep specialist
Your sleep doctor thinks you have obstructive sleep apnea
You do not have other sleep disorders
You do not have other serious medical conditions, such as heart disease or lung disease

How to Prepare for the Test
Do not take any sleep medicine and do not drink alcohol or caffeinated beverages before the test.

Why the Test Is Performed
The test is done to diagnose possible sleep disorders, including obstructive sleep apnea (OSA). Often, OSA is suspected because of the following symptoms:

Daytime sleepiness (falling asleep during the day)
Loud snoring
Periods of breath holding, followed by gasps or snorts
Restless sleep

Other sleep disorders that polysomnography may be used to diagnose are:
Narcolepsy
Periodic limb movements disorder (moving the legs often during sleep)
REM behavior disorder (a condition in which people physically "act out" their dreams)

Normal Results
A sleep study keeps track of:
How often you stop breathing for at least 10 seconds (called apnea)
How often your breathing is partly blocked for 10 seconds (called hypopnea)

Results are most often reported using the Apnea-Hypopnea Index (AHI). An AHI of less than 5 is considered normal.

A normal test result also shows normal patterns of brain waves and muscle movements during sleep.

The sleep specialist must also look at other findings from the sleep study, as well as the medical history and physical exam to make the diagnosis and decide on treatment. A sleep study can also help diagnose narcolepsy.

Polysomnography is a sleep study. A sleep study monitors you as you sleep, or try to sleep.
There are two states of sleep:
Rapid eye movement (REM) sleep is when you dream. Your muscles (except your eyes and breathing muscles) do not move during this stage of sleep.

Non-rapid eye movement (NREM) sleep has four stages that can be detected by brain electrical activity (EEG) waves.

REM sleep alternates with NREM sleep about every 90 minutes. A person with normal sleep usually has four to five cycles of REM and NREM sleep during a night.

A sleep study measures your sleep cycles and stages by recording:
Air flow in and out of the lungs during breathing
Blood oxygen levels
Body position
Brain waves (EEG)
Breathing effort and rate
Electrical activity of muscles
Eye movement
Heart rate

How the Test Is Performed
AT A SLEEP CENTER
The most common type of sleep study is performed at a special sleep center. You will be asked to arrive about 2 hours before bedtime. You will sleep in a bed at the center.

Many sleep centers have rooms that are similar to hotel rooms, so that you are in a comfortable bedroom. The test is often done during the night so that your normal sleep patterns can be studied.

The health care provider will place electrodes on your chin, scalp, and the outer edge of your eyelids. These must remain in place while you sleep.

Signals from the electrodes are recorded while you are awake (with your eyes closed) and during sleep. The time it takes you to fall asleep is measured, as well as the time it takes you to enter REM sleep.

Monitors to record your heart rate and breathing will be attached to your chest. These also must stay in place while you sleep. A specially trained health care provider will observe you while you sleep and note any changes in your breathing or heart rate. The number of times that you either stop breathing or almost stop breathing will be measured.

In some sleep study centers, a video camera records your movements during sleep.

AT HOME
Portable sleep study devices that can be used in the home instead of at a sleep center are available to help diagnose sleep apnea. You go to a sleep center to pick up the device, or a trained therapist comes to your home to set up the device.
Portable devices are best used when:

You are under the care of a sleep specialist
Your sleep doctor thinks you have obstructive sleep apnea
You do not have other sleep disorders
You do not have other serious medical conditions, such as heart disease or lung disease

How to Prepare for the Test
Do not take any sleep medicine and do not drink alcohol or caffeinated beverages before the test.

Why the Test Is Performed
The test is done to diagnose possible sleep disorders, including obstructive sleep apnea (OSA). Often, OSA is suspected because of the following symptoms:

Daytime sleepiness (falling asleep during the day)
Loud snoring
Periods of breath holding, followed by gasps or snorts
Restless sleep

Other sleep disorders that polysomnography may be used to diagnose are:
Narcolepsy
Periodic limb movements disorder (moving the legs often during sleep)
REM behavior disorder (a condition in which people physically "act out" their dreams)

Normal Results
A sleep study keeps track of:
How often you stop breathing for at least 10 seconds (called apnea)
How often your breathing is partly blocked for 10 seconds (called hypopnea)

Results are most often reported using the Apnea-Hypopnea Index (AHI). An AHI of less than 5 is considered normal.

A normal test result also shows normal patterns of brain waves and muscle movements during sleep.

The sleep specialist must also look at other findings from the sleep study, as well as the medical history and physical exam to make the diagnosis and decide on treatment. A sleep study can also help diagnose narcolepsy.

Thank you for this absolutely wonderful post. I for one, have underwent numerous Polysomnographic evaluations in my life, the last one, I really did not do so well. A diagnosis of Hypoxic respiratory Failure, and a diagnosis with Central Sleep Apnea,and then a night on the OmniLab Advanced PAP Titration system were the result of the last Polysomnographic Evaluation. I would end up having the lowest oxygen desaturation of 46% and also after that one, being that this was prior to the PAP titration, I was very disorientated, and had a really bad flare up in my Neurological status, and I almost ended up in the ER which would have been just next door to the Polysomnographic Laboratory, or PSG Laboratory. Thankfully, a nurse came down to the PSG laboratory, and she was able to assist me, and then, I was placed onto PAP Therapy Quite immediately. You see, even before, I had underwent the PSG the last one that is, I had a Respironics CPAP machine. And, when I was off of it during the night, I would always wake up disorientated, and a perfect resemblance of the DRUNK YOU DO NOT WANT TO SEE. I have my own patient monitor, and I've seen oxygen desaturations to even lower than 46% and into as low as the teens and a couple of times in the single digits. It is an absolute blessing that I ever woke up from those, but Thankfully my patient monitoring equipment has alarms on it, and so the volume set at the maximum volume, and the monitor sitting right by my ear, is certainly what I personally believe has kept me alive. My Polysomnographic Evaluation that I had, the last one anyways, was DEC 9, 2014 and it was at Good Samaritan Hospital in Lexington KY and in that hospital, they do not use ETCO2 which sucks, because I really think that it should be used at least for patients who have the diagnosis of Neuromuscular disorders. I cannot breathe as deep as most people, due to my neuromuscular weakness, so I have to breathe faster. You would think that you were looking at a baby's Polysomnographic evaluation, because my respiratory rate is commonly around 40-60BPM due to my low Tidal Volumes. It is this reason, that I now have not just a CPAP, but a VPAP machine. Its a ResMed S9 VPAP Auto. It is a very very nice machine. I just wish It had Waveforms on the Display screen like the Trillogy Ventilators do by Philips Respironics. I know how to read and understand Ventilatory Waveforms pretty well due to my profound experience around ventilators.

I want people to know, that Having a Polysomnographic Evaluation is NOT something they should really be scared of, unless they are already using a PAP therapy machine, and theymust undergo Pre-PAP titration PSG which means, they are not on PAP therapy for the first portion of their exam, and unless being off PAP Therapy results in severe severe consequences, including Judgement impairment, and other Mental Nightmares. You do NOT want to deal with those. but as for what to expect, nothing is uncomfortable. Just be sure to warn the RPSGT if you are already on PAP, and if being ofrf PAP during your sleep results in severe impairment, and like I did, if you have memory lapses, when off PAP, Please do what I did, and Inform them, that if something were to happen, and you were to become violent if your judgement and cognition were to become impaired, you do not mean to be agressive, or violent. I did that during the last Polysomnographic Evaluation. I informed the RPSGT who's name was Chris, that I do not have a tendancy to become violent, but being that when I am off PAP, I am severely impaired, I do not have good judgement, I might, and I would not purposely become violent with the intention of physical harm. He understood me, and it was a good thing that he did. I do not want to go into details, but let's just say, Me and Severe Hypoxia do NOT do well at all. I want to thank you for posting this information in regards to PSG evaluations, and when/why/how they might be performed.

It is not painful, and can be really pleasant if you know what is happening like I do. If you know what to expect however, It will help make your experience MUCH MORE PLEASANT.

I appreciate the comic relief, but what is the point of this article? Really, just what is the point of this magically appearing in a newspaper 30 years after CPAP was invented?

The NYT is supposed to be a newspaper, meaning they are supposed to be giving us the headlines and the news, not regurgitating factoids that are 30 years old.

Here's a "news flash" for them. That's not news. Because it is yesterday's news. Something to wrap fish in.

Unfortunately, some "journalists" are only paid by column inches, rather than whether what they put in those inches has any meaning. OK, it might be helpful to the uninformed or the ignorant that happen to stumble over it, and it might set them on a path that leads to improving their health. But getting off their butts and moving around instead of sitting and reading what is an otherwise useless waste of time for anyone not suffering from SA might improve their health even more.

You also expect clarity, thoroughness, and accuracy from the NYT. We didn't get much of any of those here. Two states of sleep my eye. Oversimplify much? Oversimplification is not that far away from being nothing more than misleading misinformation. Were I the publisher, I would fire that "reporter" on general principles. Learn to bear down a little, NYT; you have a reputation to uphold, or at least win back.

Last time I saw a NYT Sunday paper it was about 6 feet thick. So I think there is probably room to put stuff like this alongside gardening news, or highlights from yesterday's tea parties. Every year people get a year older, and sometimes along with that comes conditions that are very new news to the people that have them. So repeat printing of stuff like this remains fresh news to someone that needs it.

INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.